Pharmaceutical composition for treating tumor

ABSTRACT

Disclosed herein is a method for treating tumor, comprising administering a liposomal composition comprising eribulin or a pharmaceutically acceptable salt thereof and a PD-1 antagonist to a patient in need thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese patent application No.2019-138041 filed on Jul. 26, 2019, the disclosure of which is hereinincorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a pharmaceutical composition fortreating tumor.

BACKGROUND

Eribulin represented by formula (I) is used as a therapeutic agent forbreast cancer and soft tissue tumor.

Patent Literature 1 discloses eribulin or a pharmaceutically acceptablesalt thereof and a method of producing the same. Patent Literatures 2and 3 disclose methods for producing eribulin and eribulin mesylate,which is a mesylate (methanesulfonate) thereof. Patent Literature 4discloses a method of inhibiting growth of cancer in a patient byadministering eribulin or a pharmaceutically acceptable salt thereof tothe patient. Patent Literature 5 discloses a method of treating cancerin a patient by administering eribulin or a pharmaceutically acceptablesalt thereof to the patient in combination with a certain secondanticancer agent. Patent Literature 6 discloses a method of treatingcancer in a patient by administering eribulin or a pharmaceuticallyacceptable salt thereof to the patient in combination with a secondtherapeutic approach. Patent Literatures 7 and 8 disclose liposomalcompositions comprising eribulin mesylate. Patent Literature 9 disclosesa method for treating breast cancer, comprising administering acombination of eribulin or a pharmaceutically acceptable salt thereofand a programmed cell death 1 protein (PD-1) antagonist.

PD-1 is recognized as an important factor in maintenance ofimmunoregulation and peripheral tolerance. PD-1 is moderately expressedin naive T cells, B cells, and NK T cells, and upregulated by T/B cellreceptor signal transduction in lymphocytes, monocytes, and myeloidcells (Non Patent Literature 1). Meanwhile, PD-L1 is expressed invarious cancer cells or T/B cells, macrophages, mDCs, plasmacytoidDCs:(pDCs), bone marrow mast cells, and the like.

The two known PD-1 ligands PD-L1 (B7-H1) and PD-L2 (B7-DC) are expressedin human cancer occurring in various tissues. For example, in a largeamount of sample sets of ovarian cancer, renal cancer, colorectalcancer, pancreatic cancer, liver cancer, and melanoma, the PD-L1expression has been shown to correlate with poor prognosis and decreasedoverall survival, regardless of subsequent treatment (Non PatentLiteratures 2 to 13). Similarly, it was found that the PD-1 expressionin tumor-infiltrating lymphocytes is characteristic of functionallyimpaired T cells in breast cancer and melanoma (Non Patent Literatures14 to 15) and correlates with poor prognosis in kidney cancer (NonPatent Literature 16). Therefore, it has been proposed to block theimmunosuppression mechanism that cancer cells bring, such as theinteraction of tumor cells expressing PD-L1 with T cells expressingPD-1, and thereby bring the immune response to tumor.

Several monoclonal antibodies that inhibit the interaction between PD-1and either or both of PD-1 ligands PD-L1 and PD-L2 are under clinicaldevelopment for treating cancer. It has been proposed that the efficacyof such antibodies may be increased when administered in combinationwith another approved or experimental cancer therapy, for example,radiation, surgery, a chemotherapeutic agent, a targeted therapy, anagent that inhibits another signaling pathway that is dysregulated intumor, and another immunostimulant.

-   Patent Literature 1: WO 99/65894-   Patent Literature 2: WO 2005/118565-   Patent Literature 3: WO 2011/094339-   Patent Literature 4: U.S. Pat. No. 6,469,182-   Patent Literature 5: U.S. Application Publication No. 2006/104984-   Patent Literature 6: U.S. Pat. No. 6,653,341-   Patent Literature 7: WO 2010/113984-   Patent Literature 8: WO 2017/188350-   Patent Literature 9: WO 2016/141209-   Non Patent Literature 1: Sharpe, A. H, Wherry, E. J., Ahmed R., and    Freeman G. J., The function of programmed cell death 1 and its    ligands in regulating autoimmunity and infection. Nature Immunology    (2007); 8: 239-245.-   Non Patent Literature 2: Dong H et al., Tumor-associated B7-H1    promotes T-cell apoptosis: a potential mechanism of immune evasion.    Nat Med. 2002 August; 8(8): 793-800.-   Non Patent Literature 3: Yang et al., PD-1 interaction contributes    to the functional suppression of T-cell responses to human uveal    melanoma cells in vitro. Invest Ophthalmol Vis Sci. 2008 June; 49(6    (2008): 49: 2518-2525.-   Non Patent Literature 4: Ghebeh et al., The B7-H1 (PD-L1) T    lymphocyte-inhibitory molecule is expressed in breast cancer    patients with infiltrating ductal carcinoma: correlation with    important high-risk prognostic factors. Neoplasia (2006) 8: 190-198.-   Non Patent Literature 5: Hamanishi J et al., Programmed cell death 1    ligand 1 and tumor-infiltrating CD8+T lymphocytes are prognostic    factors of human ovarian cancer. Proceeding of the National Academy    of Sciences (2007): 104: 3360-3365.-   Non Patent Literature 6: Thompson R H et al., Significance of B7-H1    overexpression in kidney cancer. Clinical genitourin Cancer (2006):    5: 206-211.-   Non Patent Literature 7: Nomi, T. Sho, M., Akahori, T., et al.,    Clinical significance and therapeutic potential of the programmed    death-1 ligand/programmed death-1 pathway in human pancreatic    cancer. Clinical Cancer Research (2007); 13: 2151-2157.-   Non Patent Literature 8: Ohigashi Y et al., Clinical significance of    programmed death-1 ligand-1 and programmed death-1 ligand 2    expression in human esophageal cancer. Clin. Cancer Research (2005):    11: 2947-2953.-   Non Patent Literature 9: Inman et al., PD-L1 (B7-H1) expression by    urothelial carcinoma of the bladder and BCG-induced granulomata:    associations with localized stage progression. Cancer (2007): 109:    1499-1505.-   Non Patent Literature 10: Shimauchi T et al., Augmented expression    of programmed death-1 in both neoplasmatic and nonneoplastic CD4+    T-cells in adult T-cell Leukemia/Lymphoma. Int. J. Cancer (2007):    121: 2585-2590.-   Non Patent Literature 11: Gao et al., Overexpression of PD-L1    significantly associates with tumor aggressiveness and postoperative    recurrence in human hepatocellular carcinoma. Clinical Cancer    Research (2009) 15: 971-979.-   Non Patent Literature 12: Nakanishi J., Overexpression of B7-H1    (PD-L1) significantly associates with tumor grade and postoperative    prognosis in human urothelial cancers. Cancer Immunol    Immunother. (2007) 56: 1173-1182.-   Non Patent Literature 13: Hino et al., Tumor cell expression of    programmed cell death-1 is a prognostic factor for malignant    melanoma. Cancer (2010): 116: 1757-1766.-   Non Patent Literature 14: Ghebeh H., Foxp3+ tregs and B7-H1+/PD-1+T    lymphocytes co-infiltrate the tumor tissues of high-risk breast    cancer patients: implication for immunotherapy. BMC Cancer. 2008    Feb. 23; 8:57.-   Non Patent Literature 15: Ahmadzadeh M. et al., Tumor    antigen-specific CD8 T cells infiltrating the tumor express high    levels of PD-1 and are functionally impaired. Blood (2009) 114:    1537-1544.-   Non Patent Literature 16: Thompson R H et al., PD-1 is expressed by    tumor infiltrating cells and is associated with poor outcome for    patients with renal carcinoma. Clinical Cancer Research (2007) 15:    1757-1761.

SUMMARY

The present invention is directed to provide a new pharmaceuticalcomposition for treating tumor.

The present inventors have studied diligently and, as a result, foundthat the combined administration of a liposomal composition comprisingeribulin or a pharmaceutically acceptable salt thereof and a PD-1antagonist exhibits unexpected antitumor effect, thereby completing thepresent invention.

Accordingly, the present disclosure is as follows.

[1] A pharmaceutical composition for treating tumor, comprising aliposomal composition comprising eribulin or a pharmaceuticallyacceptable salt thereof, wherein the pharmaceutical composition isadministered in combination with a PD-1 antagonist.[2] A pharmaceutical composition for treating tumor, comprising a PD-1antagonist, wherein the pharmaceutical composition is administered incombination with a liposomal composition comprising eribulin or apharmaceutically acceptable salt thereof.[3] The pharmaceutical composition according to [1] or [2] above,wherein the liposomal composition comprising eribulin or apharmaceutically acceptable salt thereof and the PD-1 antagonist areadministered simultaneously, separately, continuously, or at a timeinterval.[4] The pharmaceutical composition according to any of [1] to [3] above,wherein eribulin or the pharmaceutically acceptable salt thereof iseribulin mesylate.[5] The pharmaceutical composition according to any of [1] to [4] above,wherein the PD-1 antagonist is an anti-PD-1 antibody.[6] The pharmaceutical composition according to [5] above, wherein theanti-PD-1 antibody is selected from the group consisting of nivolumab,pembrolizumab, cemiplimab, sintilimab, and toripalimab.[7-1] The pharmaceutical composition according to any of [1] to [6]above, wherein the tumor is selected from the group consisting of breastcancer, gastric cancer, esophageal cancer and small cell lung cancer.[7-2] The pharmaceutical composition according to any of [1] to [6]above, wherein the tumor is breast cancer.[8] A therapeutic agent for tumor, comprising a liposomal compositioncomprising eribulin or a pharmaceutically acceptable salt thereofwherein the pharmaceutical composition is administered in combinationwith a PD-1 antagonist.[9] A therapeutic agent for tumor, comprising a PD-1 antagonist, whereinthe therapeutic agent is administered in combination with a liposomalcomposition comprising eribulin or a pharmaceutically acceptable saltthereof.[10] The therapeutic agent according to [8] or [9] above, wherein theliposomal composition comprising eribulin or a pharmaceuticallyacceptable salt thereof and the PD-1 antagonist are administeredsimultaneously, separately, continuously, or at a time interval.[11] The therapeutic agent according to any of [8] to [10] above,wherein eribulin or the pharmaceutically acceptable salt thereof iseribulin mesylate.[12] The therapeutic agent according to any of [8] to [11] above,wherein the PD-1 antagonist is an anti-PD-1 antibody.[13] The therapeutic agent according to [12] above, wherein theanti-PD-1 antibody is selected from the group consisting of nivolumab,pembrolizumab, cemiplimab, sintilimab, and toripalimab.[14-1] The therapeutic agent according to any of [8] to [13] above,wherein the tumor is selected from the group consisting of breastcancer, gastric cancer, esophageal cancer and small cell lung cancer.[14-2] The therapeutic agent according to any of [8] to [13] above,wherein the tumor is breast cancer.[15] A method for treating tumor, comprising administering a liposomalcomposition comprising eribulin or a pharmaceutically acceptable saltthereof and a PD-1 antagonist to a patient in need thereof.[16] The method according to [15] above, wherein the liposomalcomposition comprising eribulin or a pharmaceutically acceptable saltthereof and the PD-1 antagonist are administered simultaneously,separately, continuously, or at a time interval.[17] The method according to [15] or [16] above, wherein eribulin or thepharmaceutically acceptable salt thereof is eribulin mesylate.[18] The method according to any of [15] to [17] above, wherein the PD-1antagonist is an anti-PD-1 antibody.[19] The method according to [18] above, wherein the anti-PD-1 antibodyis selected from the group consisting of nivolumab, pembrolizumab,cemiplimab, sintilimab, and toripalimab.[20-1] The method according to any of [15] to [19] above, wherein thetumor is selected from the group consisting of breast cancer, gastriccancer, esophageal cancer and small cell lung cancer.[20-2] The method according to any of [15] to [19] above, wherein thetumor is breast cancer.[21] Use of eribulin or a pharmaceutically acceptable salt thereof inthe manufacture of a pharmaceutical composition for treating tumor,wherein the pharmaceutical composition is administered in combinationwith a PD-1 antagonist.[22] Use of a PD-1 antagonist in the manufacture of a pharmaceuticalcomposition for treating tumor, wherein the pharmaceutical compositionis administered in combination with a liposomal composition comprisingeribulin or a pharmaceutically acceptable salt thereof.[23] The use according to [21] or [22] above, wherein the liposomalcomposition comprising eribulin or a pharmaceutically acceptable saltthereof and the PD-1 antagonist are administered simultaneously,separately, continuously, or at a time interval.[24] The use according to any of [21] to [23] above, wherein eribulin orthe pharmaceutically acceptable salt thereof is eribulin mesylate.[25] The use according to any of [21] to [24] above, wherein the PD-1antagonist is an anti-PD-1 antibody.[26] The use according to [25] above, wherein the anti-PD-1 antibody isselected from the group consisting of nivolumab, pembrolizumab,cemiplimab, sintilimab, and toripalimab.[27-1] The use according to any of [21] to [26] above, wherein the tumoris selected from the group consisting of breast cancer, gastric cancer,esophageal cancer and small cell lung cancer.[27-2] The use according to any of [21] to [26] above, wherein the tumoris breast cancer.[28] A liposomal composition comprising eribulin or a pharmaceuticallyacceptable salt thereof for use in tumor treatment, wherein theliposomal composition is administered in combination with a PD-1antagonist.[29] A PD-1 antagonist for use in tumor treatment, wherein the PD-1antagonist is administered in combination with a liposomal compositioncomprising eribulin or a pharmaceutically acceptable salt thereof.[30] The liposomal composition or PD-1 antagonist for use according to[28] or [29] above, wherein the liposomal composition comprisingeribulin or a pharmaceutically acceptable salt thereof and the PD-1antagonist are administered simultaneously, separately, continuously, orat a time interval.[31] The liposomal composition or PD-1 antagonist for use according toany of [28] to [30] above, wherein eribulin or the pharmaceuticallyacceptable salt thereof is eribulin mesylate.[32] The liposomal composition or PD-1 antagonist for use according toany of [28] to [31] above, wherein the PD-1 antagonist is an anti-PD-1antibody.[33] The liposomal composition or PD-1 antagonist for use according to[32] above, wherein the anti-PD-1 antibody is selected from the groupconsisting of nivolumab, pembrolizumab, cemiplimab, sintilimab, andtoripalimab.[34-1] The liposomal composition or PD-1 antagonist for use according to[28] to [33] above, wherein the tumor is selected from the groupconsisting of breast cancer, gastric cancer, esophageal cancer and smallcell lung cancer.[34-2] The liposomal composition or PD-1 antagonist for use according to[28] to [33] above, wherein the tumor is breast cancer.[35] A kit for treating tumor, comprising a formulation comprising aliposomal composition comprising eribulin or a pharmaceuticallyacceptable salt thereof and a formulation comprising a PD-1 antagonist.[36] The kit according to [35] above, wherein the liposomal compositioncomprising eribulin or a pharmaceutically acceptable salt thereof andthe PD-1 antagonist are administered simultaneously, separately,continuously, or at a time interval.[37] The kit according to [35] or [36] above, wherein eribulin or thepharmaceutically acceptable salt thereof is eribulin mesylate.[38] The kit according to any of [35] to [37] above, wherein the PD-1antagonist is an anti-PD-1 antibody.[39] The kit according to [38] above, wherein the anti-PD-1 antibody isselected from the group consisting of nivolumab, pembrolizumab,cemiplimab, sintilimab, and toripalimab.[40-1] The kit according to any of [35] to [39] above, wherein the tumoris selected from the group consisting of breast cancer, gastric cancel;esophageal cancer and small cell lung cancer.[40-2] The kit according to any of [35] to [39] above, wherein the tumoris breast cancer.[41] The pharmaceutical composition according to any of [1] to [7-2]above or therapeutic agent according to any of [8] to [14-2] above,further comprising a pharmaceutically acceptable carrier.

The combined administration of a liposomal composition comprisingeribulin or a pharmaceutically acceptable salt thereof and a PD-1antagonist exhibits unexpected antitumor effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating effect of treatment with a combination ofa liposomal formulation comprising eribulin mesylate at a dose of 0.1mg/kg and an anti-PD-1 antibody on tumor growth.

FIG. 2 is a graph illustrating effect of treatment with a combination ofa liposomal formulation comprising eribulin mesylate at a dose of 0.1mg/kg and an anti-PD-1 antibody on T×5.

FIG. 3 is a graph illustrating effect of treatment with a combination ofa liposomal formulation comprising eribulin mesylate at a dose of 0.3mg/kg and an anti-PD-1 antibody on tumor growth.

FIG. 4 is a graph illustrating effect of treatment with a combination ofa liposomal formulation comprising eribulin mesylate at a dose of 0.3mg/kg and an anti-PD-1 antibody on T×5.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below. Thefollowing embodiments are illustrations for the purpose of describingthe present disclosure and not intended to limit the present disclosureonly to these embodiments. The present disclosure can be carried out invarious forms, unless they deviate from its spirit.

The liposomal compositions in the present disclosure comprises eribulinor a pharmaceutically acceptable salt thereof (hereinafter referred toas “eribulin or the like”).

In the present disclosure, the “pharmaceutically acceptable salt” may beeither an inorganic acid salt or an organic acid salt and is notparticularly limited, as long as it forms a salt with eribulin, andexamples thereof include hydrochloride, sulfate, citrate, hydrobromide,hydroiodide, nitrate, bisulfate, phosphate, superphosphate,isonicotinate, acetate, lactate, salicylate, tartrate, pantothenate,ascorbate, succinate, maleate, fumarate, gluconate, saccharinate,formate, benzoate, glutamate, mesylate (methanesulfonate),ethanesulfonate, benzenesulfonate, p-toluenesulfonate, and pamoate. Inone embodiment, the pharmaceutically acceptable salts are hydrochloride,sulfate, acetate, phosphate, citrate, and mesylate. In a particularembodiment, the pharmaceutically acceptable salt is mesylate.

The pharmaceutically acceptable salt of eribulin may be a salt oferibulin and aluminum, calcium, lithium, magnesium, sodium, zinc, ordiethanolamine.

In the present disclosure, examples of eribulin or the like includeeribulin mesylate.

Eribulin or the like is a compound or a salt thereof described in PatentLiterature 1 or U.S. Pat. No. 6,214,865 and has pharmacologicalactivities including antitumor and antimitotic activities. PatentLiterature 1 discloses that eribulin or the like has, as an antitumoragent, anti-tumor activity against melanoma, fibrosarcoma, monocyticleukemia, colon cancer, ovarian cancer, breast cancel; osteosarcoma,prostate cancer, lung cancer, and ras-transformed fibroblasts. Eribulinor the like is obtained by a method of production described in PatentLiteratures 1 to 3.

In the present disclosure, the “liposome” means a closed microvesiclehaving an inner phase surrounded by a lipid bilayer. The liposomesinclude small unilamellar liposomes (SUVs: small unilamellar vesicles),large unilamellar liposomes (LUVs: large unilamellar vesicles), furtherlarge unilamellar liposomes (GUVs: giant unilamellar vesicles),multi-lamellar liposomes having a plurality of concentric membranes(MLVs: multi lamellar vesicles), liposomes having a plurality ofnon-concentric, irregular membranes (MVVs: multivesicular vesicles), andthe like.

In the present disclosure, the “liposomal inner phase” means an aqueousregion surrounded by a liposomal lipid bilayer and is used synonymouslywith an “inner aqueous phase” and a “liposomal inner aqueous phase”. The“liposomal outer phase” means a region that is not surrounded by aliposomal lipid bilayer (that is, the region except the inner phase andthe lipid bilayer) when the liposome is dispersed in a liquid.

In the present disclosure, the “liposomal composition” means acomposition comprising a liposome and further comprising eribulin or thelike in the liposomal inner phase. In the present disclosure, theliposomal composition includes solid and liquid compositions.

In the present disclosure, the “liposomal dispersion liquid” means acomposition comprising a liposome in which eribulin or the like is notyet encapsulated into the liposomal inner phase.

In the present disclosure, the “liposomal preparatory liquid” means acomposition comprising a liposome in which an adjustment of the liposomeouter phase in order to encapsulate eribulin or the like into theliposome inner phase is not yet performed.

[Lipid]

In one embodiment, the liposome preferably comprises a phospholipidand/or a phospholipid derivative as a membrane component.

Examples of the phospholipid and/or phospholipid derivative includephosphatidylethanolamine, phosphatidylcholine, phosphatidylserine,phosphatidylinositol, phosphatidylglycerol, cardiolipin, sphingomyelin,ceramide phosphoryl ethanolamine, ceramidephosphorylglycerol,ceramidephosphorylglycerolphosphate,1,2-dimyristoyl-1,2-deoxyphosphatidyl choline, plasmalogen, andphosphatidate.

The phospholipid and/or phospholipid derivative may be one or acombination of two or more of these.

Fatty acid residues in the phospholipid and/or phospholipid derivativeare not particularly limited, and examples thereof include saturated orunsaturated fatty acid residues having 12 to 20 carbon atoms, andspecific examples thereof include acyl groups derived from fatty acidssuch as lauric acid, myristic acid, palmitic acid, stearic acid, oleicacid, and linoleic acid. As the phospholipid and/or phospholipidderivative, a phospholipid derived from a natural product such as eggyolk lecithin and soy lecithin, and partially hydrogenated egg yolklecithin, (fully) hydrogenated egg yolk lecithin, partially hydrogenatedsoy lecithin, and (fully) hydrogenated soybean lecithin, in whichunsaturated fatty acid residues are partially or fully hydrogenated, orthe like may be used.

The amount (molar fraction) of the phospholipid and/or phospholipidderivative, used in the preparation of the liposome, that are/is blendedis not particularly limited, and is, in one embodiment, 10 to 80% and,in a particular embodiment, 30 to 60% based on the total ribosomalmembrane components.

In the present disclosure, the liposome may comprise, as a membranecomponent, a sterol such as cholesterol and cholestanol and a fatty acidhaving a saturated or unsaturated acyl group having 8 to 22 carbon atomsas a membrane stabilizing agent, and an antioxidant such asα-tocopherol, besides the phospholipid and/or phospholipid derivative.

The amount (molar fraction) of the sterol, used in the preparation ofthe liposome, that is blended is not particularly limited, and is, inone embodiment, 1 to 60%, 10 to 50%, or 30 to 50% based on the totalliposomal membrane components.

The amount (molar fraction) of the fatty acid blended is notparticularly limited, and is, in one embodiment, 0 to 30% and 0 to 20%or 0 to 10% based on the total liposomal membrane components.

The amount (molar fraction) of the antioxidant blended is notparticularly limited, as long as an amount that provides the antioxidanteffect is added, and it is, in one embodiment, 0 to 15%, 0 to 10%, or 0to 5% based on the total liposomal membrane components.

In the present disclosure, the liposome may comprise a functional lipidor a modified lipid as a membrane component.

Examples of the functional lipid include a blood-retaining lipidderivative, a temperature change-sensitive lipid derivative, and apH-sensitive lipid derivative.

Examples of the modified lipid include a PEGylated lipid, a glycolipid,an antibody-modified lipid, and a peptide-modified lipid.

Examples of the blood-retaining lipid derivative include polyethyleneglycol derivatives (such as methoxy polyethylene glycol condensates)such as condensation products of phosphoethanolamine and methoxypolyethylene glycol: N-{carbonyl-methoxy polyethyleneglycol-2000}-1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine,N-{carbonyl-methoxy polyethyleneglycol-5000}-1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine,N-{carbonyl-methoxy polyethyleneglycol-750}-1,2-distearoyl-sn-glycero-3-phosphoethanolamine,N-{carbonyl-methoxy polyethyleneglycol-2000}-1,2-distearoyl-sn-glycero-3-phosphoethanolamine,(MPEG2000-distearoylphosphatidylethanolamine), and N-{carbonyl-methoxypolyethyleneglycol-5000}-1,2-distearoyl-sn-glycero-3-phosphoethanolamine.

The blending amount (molar fraction) of the blood-retaining lipidderivative, used in the preparation of the liposome, is not particularlylimited, and is, in one embodiment, 0 to 50%, 0 to 30%, or 0 to 20%based on the total liposomal membrane components.

Examples of the temperature change-sensitive lipid derivative includedipalmitoylphosphatidylcholine. By including a temperaturechange-sensitive lipid derivative in a liposome, it becomes possible todisrupt the liposome at a particular temperature, to change the surfaceproperties of the liposome, and the like. Furthermore, by combining itwith heating of a target site such as tumor, it becomes possible todisrupt the liposome at the target site and have an active compoundreleased at the target site, and the like.

Examples of the pH-sensitive lipid derivative includedioleoylphosphatidylethanolamine. By including a pH-sensitive lipidderivative in a liposome, it becomes possible to promote membrane fusionof the liposome and an endosome when the liposome is taken in a cell byendocytosis and improve the delivery of the active compound to thecytoplasm, and the like.

Examples of the glycolipid, antibody-modified lipid, andpeptide-modified lipid include lipids linked to a sugar, an antibody, ora peptide having an affinity for a target cell or a target tissue. Usinga modified lipid allows to deliver the liposome actively to the targetcell or the target tissue.

The composition of membrane components for liposome having a practicallyacceptable level of membrane permeability can be set by a person skilledin the art as appropriate depending on the active compound, the targettissue, and the like (see Hiroshi Kikuchi et al. “Liposome I—How toprepare and assay—(in Japanese)” Cell technology (1983) 2 (9): pp.1136-1149 and the references cited in the reference, and the like). Theliposomal composition may be used not only in targeting at a targettissue such as solid cancel; but also in the delivery of an activecompound to blood cancer or the like.

The liposomal membrane components include, in one embodiment,phospholipid, cholesterol, and a methoxy polyethylene glycolcondensation product.

[Liposomal Composition]

In the liposomal composition in the present disclosure, eribulin or thelike is encapsulated in a liposome having a lipid membrane. In theliposomal composition, eribulin or the like may be distributed in thelipid bilayer.

The liposomal composition according to the present disclosure can beobtained by a method described in Patent Literature 7.

If the liposomal composition is solid, the solid liposomal compositionmay be dissolved or suspended in a certain solvent described below toprepare a liquid liposomal composition. In case that the liposomalcomposition is a frozen solid, the frozen solid liposomal compositionmay be thawed by leaving the composition at room temperature or the liketo prepare a liquid liposomal composition.

The liposomal composition according to the present disclosure is notlimited, as long as it comprises (1) eribulin or the like. The liposomalcomposition according to the present disclosure may further comprise (2)at least one ammonium salt and (3) at least one acid, salt, base, and/oramino acid.

Examples of the at least one ammonium salt (2) include ammoniumchloride, ammonium borate, ammonium sulfate, ammonium formate, ammoniumacetate, ammonium citrate, ammonium tartrate, ammonium succinate, andammonium phosphate and, in one embodiment, the at least one ammoniumsalt (2) is ammonium sulfate, ammonium citrate, and ammonium tartrate.

As for the acid, salt, base, and/or amino acid (3), examples of the acidinclude ascorbic acid, benzoic acid, succinic acid, citric acid,glutamic acid, phosphoric acid, acetic acid, propionic acid, tartaricacid, carbonic acid, lactic acid, boric acid, maleic acid, fumaric acid,malic acid, adipic acid, hydrochloric acid, and sulfuric acid; examplesof the salt include sodium salts of the aforementioned acids, potassiumsalts of the aforementioned acids, and ammonium salts of theaforementioned acids; examples of the base includetrishydroxymethylaminomethane, ammonia, sodium hydroxide, and potassiumhydroxide; and examples of the amino acid include arginine, histidine,and glycine.

In one embodiment of the liposomal composition according to the presentdisclosure, the acid, salt, base, and/or amino acid (3) in the liposomalinner phase is hydrochloric acid, acetic acid, lactic acid, tartaricacid, succinic acid, citric acid, and phosphoric acid, sodium salts ofthe aforementioned acids, and sodium hydroxide and ammonia, and, in aparticular embodiment, the acid, salt, base, and/or amino acid (3) isacetic acid, lactic acid, tartaric acid, citric acid, and phosphoricacid, sodium salts of the aforementioned acids, and sodium hydroxide andammonia.

An example of the components of the liposomal composition is set forthin Table 1. In another specific example, 96 mg/mL sucrose may be used,instead of 9 mg/mL sodium chloride, as an osmotic agent (liposomal outerphase).

TABLE 1 Component Concentration Purpose of inclusion Eribulin mesylate0.2 mg/mL Drug HSPC^([1]) 7.1 mg/mL Lipid membrane component Cholesterol2.3 mg/mL Lipid membrane component MPEG2000-DSPE^([2]) 2.7 mg/mL Lipidmembrane component Ammonium sulfate 100 mM Liposomal inner phasecomponent Citric acid monohydrate 30 mM Liposomal inner phase componentSodium chloride 9 mg/mL Liposomal outer phase component L-histidine 1.6mg/mL Liposomal outer phase component Sodium hydroxide/hydrochloric acidq.s. pH adjuster ^([1])Hydrogenated soy phosphatidylcholine^([2])N-{carbonyl-methoxy polyethyleneglycol-2000}-1,2-distearoyl-sn-glycero-3-phosphoethanolamine(MPEG2000-distearoylphosphatidylethanolamine)

The liposomal composition according to the present disclosure may beadministered by injection (intravenous injection, intraarterialinjection, local injection), orally, nasally, transdermally,transpulmonarily, ophthalmically, and the like, and examples thereofinclude injection such as intravenous injection, subcutaneous injection,intradermal injection, intraarterial injection, as well as localinjection to a target cell and organ. Examples of the dosage form of theliposomal composition for oral administration include tablets, powders,granules, syrups, capsules, and oral solutions. Examples of the dosageform of the liposomal composition for parenteral administration includeinjections, drip infusions, ophthalmic liquids, ointments,suppositories, suspensions, cataplasms, lotions, aerosols, and plasters,and, in one embodiment, the liposomal composition for parenteraladministration is an injection or a drip infusion. The liposomalcomposition according to the present disclosure may be formulated by amethod, for example, described in Japanese Pharmacopoeia (JP) 17thedition, United States Pharmacopoeia (USP), or European pharmacopoeia(EP).

In a case that the liposomal composition is a liquid, the liposomalcomposition may be used as it is. To use the liposomal composition as amedicine, for example, a solvent may be injected by a physician or apatient into a vial in which a solid formulation is encapsulated to dosuch preparation upon use. A solid formulation obtained by freezing aliquid liposomal composition may be stored in a frozen state and thawedby leaving at room temperature or thawed rapidly with heating back intoa liquid upon use to be used as a liquid.

The dose upon administration of the liposomal composition alone varymarkedly depending on the kind of the target disease, the age, sex, bodyweight of the patient, the severity of symptoms, and the like. Theliposomal composition is administered, for example, at 0.1 to 10 mg/m²(body surface) in terms of eribulin mesylate per day for an adult. Inone embodiment, the liposomal composition is administered at a dose of0.5 to 3 mg/m² (body surface) in terms of eribulin mesylate once every 1week, 2 weeks, or 3 weeks. In a particular embodiment, the liposomalcomposition is more preferably administered at a dose of 0.5 to 2 mg/m²(body surface) in terms of eribulin mesylate once every 1 week, 2 weeks,or 3 weeks.

In another aspect, the liposomal composition is preferably administeredat a dose of approximately 1.5 mg/m² (body surface) in terms of eribulinmesylate once every 1 week, 2 weeks, or 3 weeks.

More specifically, the liposomal composition is administeredintravenously at 0.5 to 1.4 mg/m² on day 1 of a 21-day cycle oradministered intravenously at 0.5 to 1.5 mg/m² on day 1 and day 15 of a28-day cycle in terms of eribulin mesylate.

Eribulin or the like contained in the liposomal composition may beadministered once a day or in several divided daily doses.

The liposomal composition may be a liposomal composition comprising, forexample, 0.01 to 300 mg/mL of eribulin or the like in the liposomalinner phase.

The liposomal composition is formulated, for example, as an injectioncomprising 0.20 mg/mL eribulin mesylate (0.18 mg/mL eribulin)incorporated in a liposome having a lipid membrane consisting of HSPC,cholesterol, and MPEG2000-DSPE. Such an injection may comprise sucroseor sodium chloride as an isotonizing agent, ammonium sulfate, citricacid, and L-histidine, and sodium hydroxide and hydrochloric acid toadjust pH. The injection is directly administered to a patient ordiluted with physiological saline to a concentration in the range of0.0035 mg/mL or higher and lower than 0.2 mg/mL before theadministration to a patient.

The PD-1 antagonist in the present disclosure may comprise any compoundor biological molecule that blocks the binding of PD-L1 expressed incancer cells to PD-1 expressed in immune cells (T cells, B cells, ornatural killer T (NKT) cells), or that blocks the binding of PD-L2expressed in cancer cells to PD-1 expressed in immune cells. The PD-1antagonist blocks the binding of human PD-L1 to human PD-1 and, in oneembodiment, blocks the binding of both human PD-L1 and PD-L2 to humanPD-1. The amino acid sequence of human PD-1 can be found in NCBI LocusNo.: NP_005009. The amino acid sequences of human PD-L1 and PD-L2 can befound in NCBI Locus No: NP_054862 and NP_079515, respectively.

The PD-1 antagonist useful in the present disclosure may comprise amonoclonal antibody (mAb) or an antigen-binding fragment thereof thatspecifically binds to PD-1 or PD-L1 or that specifically binds to humanPD-1 or human PD-L1. The mAb may be a human antibody, a humanizedantibody, or a chimeric antibody and may comprise a human constantregion. The human constant region is selected from the group consistingof IgG1, IgG2, IgG3, and IgG4 constant regions and, in one embodiment,the human constant region is an IgG1 or IgG4 constant region. Theantigen-binding fragment may be selected from the group consisting ofFab, Fab′-SH, F(ab)₂, scFv, and Fv fragment.

An example of useful PD-1 antagonists is an anti-PD-1 antibody, whichis, in one embodiment, an anti-human PD-1 antibody and, in a particularembodiment, an anti-human PD-1 monoclonal antibody (anti-human PD-1mAb). Examples of the human PD-1-binding mAb binding are described inU.S. Pat. Nos. 7,488,802, 7,521,051, 8,008,449, 8,354,509, 8,168,757, WO2004/004771, WO 2004/072286, WO 2004/056875, and US Patent ApplicationPublication No. 2011/0271358. Anti-human PD-1 monoclonal antibodiesuseful as the PD-1 antagonist according to the present disclosureinclude nivolumab, pembrolizumab, cemiplimab, sintilimab, andtoripalimab.

The PD-1 antagonist according to the present disclosure may beadministered by injection (intravenous injection, intraarterialinjection, local injection), orally, nasally, transdermally,transpulmonarily, ophthalmically, and the like and examples thereofinclude injection such as intravenous injection, subcutaneous injection,intradermal injection, intraarterial injection, as well as localinjection to target cells and organ. Examples of the dosage form of thePD-1 antagonist for oral administration include tablets, powders,granules, syrups, capsules, and oral solutions. Examples of the dosageform of the PD-1 antagonist for parenteral administration includeinjections, drip infusions, ophthalmic liquids, ointments,suppositories, suspensions, cataplasms, lotions, aerosols, and plastersand in one embodiment, the dosage form of the PD-1 antagonist forparenteral administration is an injection or a drip infusion. The PD-1antagonist according to the present disclosure may be formulated by amethod, for example, described in Japanese Pharmacopoeia (JP) 17thedition, United States Pharmacopoeia (USP), or European pharmacopoeia(EP).

If the PD-1 antagonist according to the present disclosure is ananti-PD-1 antibody, the anti-PD-1 antibody may be provided as a liquidpreparation or prepared by rehydrating freeze-drying powder with sterilewater for injection before use.

Upon administration of an anti-human PD-1 mAb alone as the PD-1antagonist to a patient, the dose thereof varies markedly depending onthe kind of the target disease, the age, sex, body weight of thepatient, the severity of symptoms, and the like. The anti-human PD-1 mAbis administered, for example, at a dose of 1, 2, 3, 5, or 10 mg/kg atintervals of approximately 14 days (±2 days), approximately 21 days (±2days), or approximately 30 days (±2 days).

When pembrolizumab is administered as the PD-1 antagonist, pembrolizumabis, for example, administered intravenously at a dose selected from thegroup consisting of 1 mg/kg Q2W, 2 mg/kg Q2W, 3 mg/kg Q2W, 5 mg/kg Q2W,10 mg of Q2W, 1 mg/kg Q3W, 2 mg/kg Q3W, 3 mg/kg Q3W, 5 mg/kg Q3W, and 10mg Q3W. Pembrolizumab is administered as a liquid medicine, for example,comprising 25 mg/ml pembrolizumab, 7% (w/v) sucrose, and 0.02% (w/v)polysorbate 80 in a 10 mM histidine buffer, pH 5.5, and a selected doseof the medicine is administered by IV injection over a period ofapproximately 30 minutes.

When nivolumab is administered as the PD-1 antagonist, nivolumab is, forexample, administered intravenously at a dose selected from the groupconsisting of 1 mg/kg Q2W, 2 mg/kg Q2W, and 3 mg/kg Q2W.

The doses of the liposomal composition and the PD-1 antagonist in thecombined administration of the present disclosure may usually be set atdoses lower than the doses when they are administered alone. Specificdoses, administration routes, administration frequencies, andadministration cycles are determined as appropriate in consideration ofthe kind of the target disease, the age, sex, body weight of thepatient, the severity of symptoms, and the like.

The mode of administration of the liposomal composition and the PD-1antagonist in the present disclosure is not particularly limited, aslong as the liposomal composition and the PD-1 antagonist areadministered in combination when they are administered. For example, theliposomal composition and the PD-1 antagonist are administered to apatient simultaneously, separately, continuously, or at a time interval.Here, “simultaneously” means that each component is administered in thesame period of time or strictly simultaneously or via the sameadministration route. “Separately” means that each component isadministered at different dose intervals or frequencies or via differentadministration routes. “Continuously” means that each component isadministered via the same administration route or differentadministration routes in any order within a certain period of time. “Ata time interval” means that each component is administered via the sameadministration route or different administration routes, with eachcomponent administered at a time interval. When the PD-1 antagonist isadministered in a period of 1 cycle of the administration of theliposomal composition or in a period in which the cycle is repeated, itis considered that both are administered in combination.

Tumors to be treated in the present disclosure are, for example, breastcancer, gastric cancer, esophageal cancer, small cell lung cancer,colorectal cancer, and kidney cancer.

EXAMPLES [Example 1] Antitumor Effect of Combined Administration of LowDose of Eribulin Mesylate (0.1 mg/kg) or Low Dose of Eribulin MesylateLiposomal Formulation (0.1 mg/kg) and Anti-Mouse PD-1 Antibody inSyngeneic Transplantation Model of Murine Breast Cancer 4T1 Cell Line(Pgp-KO 4T1) with P Glycoprotein Knock-Out

A P glycoprotein-knockout cell line produced from murine breast cancer4T1 cells (purchased from ATCC) was cultured using RPMI1640 medium(SIGMA) containing 10% of FBS (fetal bovine serum), 1 mM sodiumpyruvate, and antibiotics, under conditions at 37° C. in a 5% carbondioxide gas incubator. The cells were collected using trypsin-EDTA whenthe cells reached to approximately 80% confluency. The medium describedabove (RPMI1640) was added to the collected cells, a suspension wasprepared at 1.0×10⁷ cells/mL, and 0.1 mL of the suspension wassubcutaneously transplanted at the right body side into 6 mice(BALB/cAJcl, CLEA Japan, Inc.) per each group of the control group,eribulin mesylate alone administration group, eribulin mesylateliposomal formulation alone administration group, the anti-mouse PD-1antibody (Bio X cell) alone administration group, eribulin mesylate andanti-mouse PD-1 antibody combined administration group, and eribulinmesylate liposomal formulation and anti-mouse PD-1 antibody combinedadministration group. From day 5 post-transplantation, eribulin mesylate(0.1 mg/kg, once a week, twice in total, tail vein injection), eribulinmesylate liposomal formulation (0.1 mg/kg, once a week, twice in total,tail vein injection), and the anti-mouse PD-1 antibody (200 μg/mouse,once a week, twice in total, tail vein injection) were each administeredalone or in combination to the alone administration groups or theanti-mouse PD-1 antibody combined administration groups. No drug wasadministered to the control group. The maximum tolerated dose oferibulin mesylate liposomal formulation in mice is 2.5 mg/kg and thedose in this experiment was set very low at 0.1 mg/kg, which is 1/25 ofthe maximum tolerated dose.

The liposomal composition comprising eribulin mesylate was prepared withthe components set forth in Table 1 in accordance with the followingmethod.

<Preparation of Aqueous Solution for Liposomal Inner Phase>

Ammonium sulfate and citric acid monohydrate were dissolved and dilutedwith pure water to prepare an aqueous solution of 200 mM ammoniumsulfate/60 mM citric acid. The aqueous solution of 200 mM ammoniumsulfate/60 mM citric acid was adjusted to pH 5.5 with an aqueousammonium solution and then diluted with pure water to obtain an aqueoussolution of 100 mM ammonium sulfate/30 mM citric acid.

<Preparation of Liposomal Preparatory Liquid>

Hydrogenated soy phosphatidylcholine, cholesterol, andMPEG2000-distearoylphosphatidylethanolamine were weighted in accordancewith a weight ratio of 71:23:27, respectively. These were each dissolvedin chloroform and these solutions were mixed. Chloroform was thenevaporated under reduced pressure in a rotary evaporator to prepare alipid film. To the obtained lipid film, the prepared aqueous solutionfor liposomal inner phase heated to approximately 80° C. was added andthe resulting mixture was stirred to prepare a liposomal preparatoryliquid. Sizing was performed using an extruder (a product made by LipexBiomembranes Inc.) heated to approximately 80° C. to obtain a sizedliposomal preparatory liquid.

<Preparation of Liposomal Dispersion Liquid>

By eluting the obtained liposomal preparatory liquid through a SephadexG-50 column with an aqueous solution of 0.9% sodium chloride/10 mMhistidine (pH=7.6), the liposomal outer phase was exchanged into anaqueous solution of 0.9% sodium chloride/10 mM histidine. Afterexchanging the liposomal outer phase, the liquid was centrifuged at400,000×g for 30 minutes. After the centrifugation, re-dispersion wasperformed and the liquid volume was adjusted with an aqueous solution of0.9% sodium chloride/10 mM histidine to obtain a liposomal dispersionliquid.

<Preparation of Eribulin Mesylate Solution>

0.9% of eribulin mesylate was dissolved in an aqueous solution of sodiumchloride/10 mM histidine to obtain an eribulin mesylate solution.

<Preparation of Liposomal Composition>

The liposomal dispersion liquid and eribulin mesylate solution weremixed in a glass container and incubated in a water bath at 60° C. for 3minutes to obtain a liposomal composition with a liposomal inner phasein which eribulin mesylate was introduced. An aqueous solution of 0.9%sodium chloride/10 mM histidine was added to the liposomal compositionand filter sterilization was performed with a 0.22 μm polyvinylidenefluoride (PVDF) filter to obtain an eribulin mesylate liposomalcomposition.

On day 3, day 7, day 10, day 13, day 16, day 20, day 23, day 27, day 30,and day 34 after administration, with the starting date ofadministration being day 0, the longest diameter and the short axis ofthe tumor grown in each mouse were measured with a digimatic caliper (aproduct made by Mitutoyo Corporation).

The tumor volume was calculated in accordance with the followingformula.

Tumor volume (mm³)=longest diameter (mm)×short axis² (mm²)/2

The results of measurement of the tumor volume in each group areillustrated as mean and standard deviation (SD) in FIG. 1. Asstatistical analysis, repeated measures analysis of variance (ANOVA)followed by Dunnett's multiple comparison was conducted in comparisonwith the control group for tumor volumes on all measurement days in allgroups (*: p<0.05, ***: p<0.001). The statistical comparison between thetwo groups of eribulin mesylate and anti-mouse PD-1 antibody combinedadministration group and eribulin mesylate liposomal formulation andanti-mouse PD-1 antibody combined administration group was conducted byrepeated measures ANOVA (#: p<0.05).

As a result, the combined administration of a low dose of eribulinmesylate liposomal formulation (0.1 mg/kg) and an anti-mouse PD-1antibody exhibited a remarkable antitumor effect in comparison with thecontrol group in the Pgp-KO 4T1 syngeneic tumor transplantation model. *and *** in FIG. 1 indicate that the combined administration of eribulinmesylate liposomal formulation and the anti-mouse PD-1 antibodystatistically significantly inhibited tumor growth in comparison withthe control group. # indicates that the combined administration oferibulin mesylate liposomal formulation and the anti-mouse PD-1 antibodystatistically significantly inhibited tumor growth in comparison withthe combined administration of eribulin mesylate and the anti-mouse PD-1antibody. In contrast, no antitumor effect was observed at low doseswith eribulin mesylate (0.1 mg/kg) alone administration, eribulinmesylate liposomal formulation (0.1 mg/kg) alone administration, theanti-mouse PD-1 antibody alone administration, and even the combinedadministration of eribulin mesylate (0.1 mg/kg) and the anti-mouse PD-1antibody.

The result of comparison of the groups for the time until the tumorvolume exceeds 5 times that on the starting date of administration (T×5)in the experiment is shown in FIG. 2 and the median of T×5 in each groupand the percentage (%) thereof to the control group are set forth inTable 2. For statistical analysis, a log-rank test was conducted incomparison with the control group to calculate the Bonferroni-correctedp-value (*: p<0.05).

As a result, the combined administration of eribulin mesylate liposomalformulation (0.1 mg/kg) and the anti-mouse PD-1 antibody exhibited theeffect of extending (243%) the time of suppressing tumor growth (T×5) inPgp-KO 4T1 syngeneic tumor transplantation model. In contrast, noextension effect was observed at low doses with eribulin mesylate (0.1mg/kg) alone administration, eribulin mesylate liposomal formulation(0.1 mg/kg) alone administration, the anti-mouse PD-1 antibody aloneadministration, and further the combined administration of eribulinmesylate and the anti-mouse PD-1 antibody. * in Table 2 indicates thatthe combined administration of eribulin mesylate liposomal formulation(0.1 mg/kg) and the anti-mouse PD-1 antibody statistically significantlyextended the time of tumor growth suppression in comparison with thecontrol group.

TABLE 2 Effect of the combined administration of eribulin mesylateliposomal formulation (0.1 mg/kg) and anti-mouse PD-1 antibody on T × 5Percentage to Group T × 5 (days) control Control 10.5 100% Eribulinmesylate Alone 12.0 114% Eribulin mesylate liposomal formulation Alone11.5 110% Anti-mouse PD-1 antibody Alone 14.5 138% Eribulin mesylate +Anti-mouse 14.5 138% PD-1 antibody Combined administration Eribulinmesylate liposomal formulation + 25.5* 243% Anti-mouse PD-1 antibodyCombined administration

[Example 2] Antitumor Effect of Combined Administration of Low Dose ofEribulin Mesylate (0.3 mg/kg) or Low Dose of Eribulin Mesylate LiposomalFormulation (0.3 mg/kg) and Anti-Mouse PD-1 Antibody in Pgp-KO 4T1 CellLine Syngeneic Transplantation Model

Pgp-KO 4T1 cells were cultured with the RPMI1640 medium containing 10%FBS, 1 mM sodium pyruvate, and antibiotics under conditions at 37° C. ina 5% carbon dioxide gas incubator. The cells were collected usingtrypsin-EDTA when the cells reached to approximately 80% confluency. Themedium described above was added to the collected cells to prepare asuspension at 1.0×10⁷ cells/mL. 0.1 mL of the cell suspension wassubcutaneously transplanted at the right body side into 6 mice(BALB/cAJcl, CLEA Japan, Inc.) per each group of the control group,eribulin mesylate liposomal formulation alone administration group, theanti-mouse PD-1 antibody (Bio X cell) alone administration group, andthe combined administration of eribulin mesylate liposomal formulationand the anti-mouse PD-1 antibody. From day 4 post-transplantation,eribulin mesylate liposomal formulation (0.3 mg/kg, once a week, twicein total, tail vein injection) and the anti-mouse PD-1 antibody (200μg/mouse, once a week, twice in total, tail vein injection) were eachadministered alone or in combination to the alone administration groupsor the combined administration group. No drug was administered to thecontrol group. The liposomal composition comprising eribulin mesylatewas prepared in accordance with the method as that in Example 1.

On day 3, day 7, day 9, day 13, day 17, day 20, day 24, day 27, day 31,day 34, day 38, day 41, day 44, day 48, and day 51 after administration,with the starting date of administration being day 0, the longestdiameter and the short axis of the tumor grown in each mouse weremeasured with a digimatic caliper (a product made by MitutoyoCorporation).

The tumor volume was calculated in accordance with the followingformula.

Tumor volume (mm³)=longest diameter (mm)×short axis² (mm²)/2

The mean and standard deviation (SD) of the results of measurement ofthe tumor volume in each group are illustrated in FIG. 3 and thefrequencies of mice with tumor disappearance are set forth in Table 3.For statistical analysis, the statistical comparison between the twogroups of eribulin mesylate liposomal formulation alone administrationgroup or the anti-mouse PD-1 antibody alone administration group anderibulin mesylate liposomal formulation and anti-mouse PD-1 antibodycombined administration group was conducted by repeated measures ANOVA(t, #: p<0.05).

As a result, in the Pgp-KO 4T1 syngeneic tumor transplantation model,the combined administration of a low dose of eribulin mesylate liposomalformulation (0.3 mg/kg) and the anti-mouse PD-1 antibody exhibitedexcellent antitumor effect in comparison with eribulin mesylateliposomal formulation alone administration group or the anti-mouse PD-1antibody alone administration group. In FIG. 3, (t) indicates that thecombined administration of eribulin mesylate liposomal formulation andthe anti-mouse PD-1 antibody statistically significantly inhibited tumorgrowth in comparison with eribulin mesylate liposomal formulation aloneadministration and (#) indicates that the combined administration oferibulin mesylate liposomal formulation and the anti-mouse PD-1 antibodystatistically significantly inhibited tumor growth in comparison withthe anti-mouse PD-1 antibody alone administration. The tumordisappearance was observed in the combined administration group oferibulin mesylate liposomal formulation (0.3 mg/kg) and the anti-mousePD-1 antibody at a frequency higher than other groups.

TABLE 3 Frequency of appearance of mice with tumor disappearance in eachgroup Frequency (%) of mice with tumor Group disappearance Control 0/6(0%) Eribulin mesylate liposomal formulation Alone 1/6 (17%) Anti-mousePD-1 antibody Alone 0/6 (0%) Eribulin mesylate liposomal formulation +4/6 (67%) Anti-mouse PD-1 antibody Combined administration

The result of comparison of the groups for the time until the tumorvolume exceeds 5 times that on the starting date of administration (T×5)in the experiment is shown in FIG. 4 and the median of T×5 in each groupand the percentage (%) thereof to the control group are set forth inTable 4. For statistical analysis, a log-rank test between the 2 groupsof the combined administration group of eribulin mesylate liposomalformulation and the anti-mouse PD-1 antibody to the anti-mouse PD-1antibody, alone administration group was conducted (#: p<0.05).

As a result, in the Pgp-KO 4T1 syngeneic tumor transplantation model,the combined administration of eribulin mesylate liposomal formulation(0.3 mg/kg) and the anti-mouse PD-1 antibody exhibited the effect ofextending suppression time of tumor growth (T×5) in comparison with thecontrol group, eribulin mesylate liposomal formulation aloneadministration group, the anti-mouse PD-1 antibody alone administrationgroup. # in FIG. 4 indicates that the combined administration oferibulin mesylate liposomal formulation and the anti-mouse PD-1 antibodystatistically significantly extended suppression time of tumor growth incomparison with the anti-mouse PD-1 antibody alone administration.

TABLE 4 Effect of combined administration of eribulin mesylate liposomalformulation (0.3 mg/kg) and anti-mouse PD-1 antibody to T × 5 Group T ×5 (days) Ratio to control Control 11.5 100% Eribulin mesylate liposomalformulation Alone 33.0 287% Anti-mouse PD-1 antibody Alone 18.0 157%Eribulin mesylate liposomal formulation + >51.0# >443%  Anti-mouse PD-1antibody Combined administration

1-7. (canceled)
 8. A method for treating a tumor, comprisingadministering a liposomal composition comprising eribulin or apharmaceutically acceptable salt thereof and a PD-1 antagonist to apatient in need thereof, wherein the PD-1 antagonist is an anti-PD-1antibody, and wherein the tumor is selected from the group consisting ofgastric cancer, esophageal cancer, and small cell lung cancer.
 9. Themethod according to claim 8, wherein the liposomal compositioncomprising eribulin or a pharmaceutically acceptable salt thereof andthe PD-1 antagonist are administered simultaneously.
 10. The methodaccording to claim 8, wherein the liposomal composition comprisingeribulin or a pharmaceutically acceptable salt thereof and the PD-1antagonist are administered separately.
 11. The method according toclaim 8, wherein eribulin or the pharmaceutically acceptable saltthereof is eribulin mesylate.
 12. The method according to claim 8,wherein the anti-PD-1 antibody is selected from the group consisting ofnivolumab, pembrolizumab, cemiplimab, sintilimab, and toripalimab. 13.The method according to claim 8, wherein the tumor is gastric cancer.14. The method according to claim 12, wherein the tumor is gastriccancer.
 15. The method according to claim 8, wherein the tumor isesophageal cancer.
 16. The method according to claim 12, wherein thetumor is esophageal cancer.
 17. The method according to claim 8, whereinthe tumor is small cell lung cancer.
 18. The method according to claim12, wherein the tumor is small cell lung cancer.
 19. The methodaccording to claim 12, wherein eribulin or the pharmaceuticallyacceptable salt thereof is eribulin mesylate.
 20. The method accordingto claim 13, wherein eribulin or the pharmaceutically acceptable saltthereof is eribulin mesylate.
 21. The method according to claim 14,wherein eribulin or the pharmaceutically acceptable salt thereof iseribulin mesylate.
 22. The method according to claim 15, whereineribulin or the pharmaceutically acceptable salt thereof is eribulinmesylate.
 23. The method according to claim 16, wherein eribulin or thepharmaceutically acceptable salt thereof is eribulin mesylate.
 24. Themethod according to claim 17, wherein eribulin or the pharmaceuticallyacceptable salt thereof is eribulin mesylate.
 25. The method accordingto claim 18, wherein eribulin or the pharmaceutically acceptable saltthereof is eribulin mesylate.